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Protractors

War

Military operations frequently require surveying and navigational activities. In addition to the tasks described on those pages of this exhibit, early modern military architects used protractors to create designs for fortifications. In the 20th century, protractors were utilized to position artillery pieces. The collections are especially rich in examples from the Felsenthal Instruments Company, a Chicago manufacturer of scientific instruments that was influential from the 1940s to the 1970s.

This yellow xylonite (celluloid-like plastic) rectangular protractor is contained in a paper wrapper marked: MILITARY PROTRACTOR (/) MADE BY (/) KEUFFEL & ESSER CO. (/) NEW YORK. It is divided by degree and marked by tens from 10° to 170° and from 190° to 350°, both in the clockwise direction. An arrow points to the origin point. A small hole near the 160° mark permits a weight to be suspended so that the protractor functions as a rough clinometer, to measure angles of elevation or slope.

Four slope scales appear on the bottom edge of the instrument. These allow draftsmen to read or draw topographical contours indicating slopes in landforms of 7° and 3-1/2°; 8°, 4°, 2°, and 1°; 10°, 5°, and 2-1/2°; and 12°, 6°, 3°, and 1-1/2°, respectively. The scales for each set of slope measurements are not indicated, but they presumably are standard scales for American military engineering, such as 1:63,360 and 1:25,000.

A scale of inches divided to tenths and marked by ones from 0" to 5" appears on the interior of the protractor. Below that scale are three scales for 1", 3", and 6" to the mile, respectively. Each scale is divided in 100-yard increments. The first is marked by thousands of yards from 1,000 to 8,000; the second is marked by 500 yards from 500 to 2,500; and the third is marked by 500 yards from 500 to 1,000.

Maker's and owner's marks are near the lower edge: KEUFFEL & ESSER CO.; NEW YORK; ENG. DEPT. U.S.A. 1918. The United States Engineering Department was part of the U.S. Army Corps of Engineers in the 19th and 20th centuries. K&E began to sell this form of military protractor between 1916 and 1921, so this object may have been in use during World War I (as the markings suggest). In 1936, the protractor cost $3.50. The design of the instrument changed again between 1936 and 1943. K&E noted in the 1943 catalog that the changed form was manufactured according to the specifications of the Corps of Engineers.

This clear plastic semicircular protractor is divided by ten mils and marked by hundreds from 100 to 3,100 in both the clockwise and counterclockwise directions. It is also divided by single degrees and marked by tens from 0° to 180° in both directions. Diagonal lines extend some of the measurement markings out to the edges of the rectangle surrounding the protractor. Pinholes are at the origin point and in the upper left and right corners. The interior of the protractor has cutout stencils for a circle, triangle, square, and two oblong shapes. The middle also contains scales placed at right angles to each other. They are divided and marked by hundreds from 1,000 to 2[00]. The scales are labeled: 1:21120.

The left edge of the rectangular plastic piece is divided by tenths of an inch and marked by ones from 1 to 3. Inside the 3-inch ruler is a scale for mils divided by hundreds and marked by thousands from 5,000 to 1,000. The scale continues on the top of the rectangle, again divided by hundreds and marked by thousands from 5,000 to 1,000. The scale is labeled: 1:62500. On the right side of the top is a scale labeled: 1:20,000. It is divided and marked by hundreds from 1,000 to 2[00]. This scale also repeats on the right side of the rectangle. On the right edge of the rectangle, there is a scale divided by millimeters and marked by ones from 1 to 7. It is labeled: METRIC.

The bottom of the protractor bears a scale divided by hundreds and marked by thousands from 1,000 to 8,000. It is labeled: 1:62500. The bottom edge has a second scale, divided by hundreds and marked by five hundreds from 500 to 3,000. It is labeled: 1:21120. The name of the instrument is printed on the very bottom edge: MAP COORDINATOR AND PROTRACTOR - A-10. Donor Ben Rau dated the object to 1942.

This clear plastic semicircular protractor is divided to ten mils and marked by hundreds from 100 to 3,100 and from 3,300 to 6,300. The bottom edge is divided by quarter-yards and marked by ones from 0 to 26. There is a vernier to the left of the divisions, and the scale is given as 1:10,000. Inside the divisions is a second ruler, divided by two yards and marked by twos from -2 to 52. The scale is given as 1:20,000.

A rectangular slot inside these rulers is divided by half-inches and marked by ones from 0 to 7. A vernier is to the left of this ruler. The upper interior of the protractor contains two scales forming a right-angled point. There are ten divisions between each unit on the scales. The outer markings are by ones from 0 to 10 and are labeled: YARDS 1:20,000. The inner markings are by twos from 2 to 20; they are labeled: YARDS 1:40,000.

This clear plastic semicircular protractor is divided by tens and marked by hundreds from 100 to 3,100 mils and from 3,300 to 6,300 mils. Mils are units used in artillery and other military applications; 1,000 mils is equivalent to 56.25°. A pinhole is at the origin point. The bottom edge of the protractor is divided by hundreds and marked by five hundreds from 0 to 4,500. A small vernier appears to the left of the scale, and the scale is labeled: 1/25,000 METERS.

The interior of the protractor has a relatively small semicircular opening with a groove parallel to the origin point. Below the opening is a maker's mark: 8 INCH (/) G. FELSENTHAL & SONS, INC. (/) FAE-23. Donor Ben Rau, who worked for Felsenthal, dated the object to 1948. The form of the signature indicates it was probably manufactured for the U.S. Army in the 1950s.

This protractor is very similar to 1977.1141.12. See also 1977.1141.01, 1977.1141.02, 1977.1141.03, 1977.1141.05, 1977.1141.08, 1977.1141.09, 1977.1141.10, 1977.1141.18, 1977.1141.19, 1977.1141.20, 1977.1141.21, 1977.1141.22, 1977.1141.23, 1977.1141.24, 1977.1141.30, and 1977.1141.39.

This clear plastic rectangular protractor is divided by single degrees and marked by tens from 10° to 170° and from 190° to 350°. Pinholes near the 20° and 60° marks allow for positioning the protractor. The bottom edge is divided by tenths of an inch and marked by ones from 1" to 5". The interior of the protractor contains three scales of equal parts: 1) divided by hundreds and marked by five hundreds from 0 to 2,500 yards, for a scale of 1/20,000; 2) divided by hundreds and marked by thousands from 0 to 7,000 yards, for a scale of 1/62,500; and 3) divided by hundreds and marked by five hundreds from 0 to 2,000 meters, for a scale of 1/20,000. There are verniers to the left of the first and third scales.

Near the top of the protractor is marked: U.S. 1951. The 1951 is believed to refer to the date of the object. The maker's mark is: G. FELSENTHAL & SONS, INC. (/) PART NO. FAE-9.

This semicircular protractor is cut out from the center of a white piece of rectangular plastic. The front is marked in black print. The protractor is divided by half-degrees and marked by tens from 0° to 180° and from 180° to 360°. An arrow points to the index, or origin, point. The bottom edge of the rectangle is divided by two millimeters and marked by single centimeters from 0 to 20. The number 5731 is printed above the left side of the centimeter ruler.

The upper-left corner is divided by fifties and marked by thousands from 3000 to 1000 to 1000 to 3000. The scale is labeled: YARDS (/) RF = 1:50,000. Between the scale and protractor is printed: USMA (/) MODEL (/) 1953. The upper-right corner is divided by twenties and marked by hundreds from 5 to 1, 1000 to 1[00] to 1000, and 1 to 5. The scale is labeled: YARDS (/) RF = 1:25,000. Between the scale and protractor is printed: PROPERTY OF (/) M. T. AND G. (/) USMA.

The back of the protractor is marked in red print. The protractor is divided into units of twenty mils and marked by two hundreds from 0 to 3200 and from 3200 to 6400. An arrow points to the index point. The bottom edge of the rectangle is divided by tenths of an inch and marked by ones from 0" to 8".

The upper-left corner is divided by fifties and marked by thousands from 3,000 to 1,000 to 1,000 to 3,000. The scale is labeled: METERS (/) RF = 1:50,000. Between the scale and protractor is printed: USMA (/) MODEL (/) 1953. The upper-right corner is divided by twenties and marked by hundreds from 5 to 1, 1,000 to 1[00] to 1,000, and 1 to 5. The scale is labeled: METERS (/) RF = 1:25,000. Between the scale and protractor is printed: PROPERTY OF (/) M. T. AND G. (/) USMA.

Felsenthal Instruments Company manufactured this protractor for the United States Military Academy at West Point, N.Y. Donor Ben Rau, who worked for Felsenthal, dated the object to 1954.

This clear plastic semicircular protractor is divided by tens and marked by hundreds from 100 to 3,100 mils and from 3,300 to 6,300 mils. Mils are units used in artillery and other military applications; 1,000 mils is equivalent to 56.25°. A pinhole is at the origin point. The bottom edge of the protractor is divided by hundreds and marked by five hundreds from 0 to 8,000 yards. A small vernier appears to the left of the scale, and the scale is labeled: 1/20,000.

The interior of the protractor has a semicircular opening with a groove parallel to the origin point. Below the opening is a maker's mark: 16 INCH (/) G. FELSENTHAL & SONS, INC. (/) -CHICAGO-. The letters U.S. are printed above the origin point. Donor Ben Rau, who worked for Felsenthal, dated the object to 1942. The form of the maker's name indicates it was probably manufactured for the U.S. Army in the 1950s.

This protractor is very similar to 1977.1141.11, although the scale for plotting the distance of fired artillery is in yards rather than in meters.

This clear plastic semicircular protractor is divided by tens and marked by hundreds from 100 to 3,100 mils and from 3,300 to 6,300 mils. Mils are units used in artillery and other military applications; 1,000 mils is equivalent to 56.25°. A pinhole is at the origin point. The bottom edge of the protractor is divided by hundreds and marked by thousands from 7,000 to 0. A vernier appears to the right of the scale. The scale is labeled: 1/25,000. Superimposed on the scale is a second scale, divided by two hundreds and marked (in red) by two thousands from 0 to 14,000. A vernier appears to the left of that scale, which is labeled (in red): 1/50,000 YARDS.

The interior of the protractor has a semicircular opening with a groove parallel to the origin point. Below the opening is a maker's mark: 16 INCH (/) G. FELSENTHAL & SONS, INC. (/) -CHICAGO- (/) FAE-8. The letters U.S. are printed above the origin point. Donor Ben Rau dated the object to 1945, but the form of the signature indicates the protractor may not have been manufactured for the U.S. Army until the 1950s.

This protractor is very similar to 1977.1141.12, although the scale for plotting the distance of fired artillery is in yards rather than in meters. The red ink on this instrument is particularly vibrant. See also 1977.1141.01, 1977.1141.02, 1977.1141.03, 1977.1141.05, 1977.1141.08, 1977.1141.09, 1977.1141.10, 1977.1141.11, 1977.1141.18, 1977.1141.20, 1977.1141.21, 1977.1141.22, 1977.1141.23, 1977.1141.24, 1977.1141.30, and 1977.1141.39.

This clear plastic rectangular protractor is divided by single degrees and marked by tens from 10° to 170° and from 190° to 350°. Pinholes near the 20° and 60° marks allow for positioning the protractor. The bottom edge is divided by tenths of an inch and marked by ones from 1" to 5". The interior of the protractor contains three scales of equal parts: 1) divided by hundreds and marked by five hundreds from 0 to 2,500 yards, for a scale of 1/20,000; 2) divided by hundreds and marked by thousands from 0 to 7,000 yards, for a scale of 1/62,500; and 3) divided by hundreds and marked by five hundreds from 0 to 2,000 meters, for a scale of 1/20,000. There are verniers to the left of the first and third scales.

Near the top of the protractor is marked: U.S. 1957. The 1957 is believed to refer to the date of the object. The maker's mark is: G. FELSENTHAL & SONS, INC. (/) PART NO. FAE-9A.

This clear plastic semicircular protractor is divided by twenties and marked by two hundreds from 0 to 3,200 and from 3,200 to 6,400. A pinhole is at the origin point. The interior is labeled: ANGULAR MILS; 8016738. This protractor was item no. FAO-44. Felsenthal Instruments Company manufactured it for the U.S. Army about 1958.

The Felsenthal Instruments Company was the leading supplier of mathematical instruments to the U.S. Army Air Force and the U.S. Navy Bureau of Aeronautics, particularly during World War II (when the firm was known as G. Felsenthal & Sons). After the company ceased operations in approximately 1976, it provided a large sample of its products to the Smithsonian.